The present invention relates to a resin-encapsulated semiconductor device, and more particularly to techniques for improving the device in which a semiconductor pellet is mounted on a tabless lead frame by die bonding.
In U.S. patent application Ser. No. 845332 (filed Mar. 21, 1986), now abandoned, and the official gazette of Japanese patent application Laid-open No. 218139/1986, the inventors of the present application have previously proposed a resin-encapsulated semiconductor device which is shown as a sectional view in FIG. 1E, as a plan view in FIG. 1F and as a sectional view of essential portions in FIG. 1G.
The sectional view of FIG. 1E is taken along line 1X--1X in FIG. 1F, while the sectional view of FIG. 1G is taken along line 1Y--1Y in FIG. 1F.
As illustrated in these figures, the device 103 adopts a system wherein a semiconductor pellet (hereinbelow, simply termed "pellet") 101 is mounted on the plurality of leads 102a of a lead frame 102. More specifically, unlike the hitherto-conventional type in which the pellet 101 is secured onto a tab (sometimes called "bed" etc.) being usually square and serving to place the pellet on the central part thereof, the resin-encapsulated semiconductor device 103 is so constructed that the pellet 101 is mounted by die bonding on the lead frame 102 the pellet placing portion of which includes the plurality of leads 102a, and that a resin mold member 104 is formed by molding a resin.
At the step of the die bonding in this device 103, as illustrated in FIG. 1E, an insulating sheet 105 is bonded by a binder 105a, and the pellet 101 is fastened on the sheet 105 by a binder 106.
By the way, in FIG. 1F, numeral 107 designates bonding pads on the pellet 101, numeral 102b lead side bonding posts, and numeral 108 pieces of bonding wire.
The device 103 stated above forms a technique which is very advantageous for packaging a large-sized pellet. More specifically, even when a pellet becomes larger in size, a package for encasing the pellet cannot be enlarged because the size thereof is standardized. Therefore, with the conventional system wherein the pellet is mounted on the tab and wherein the pellet on the tab and inner leads extending toward the tab are connected by wire bonding, the leads which are buried in a resin mold member become shorter, to incur such a problem that the leads are more liable to come off the package. In contrast, with the device 103, the inner leads of the leads 102a are shaped to be very long, and the bonding strength thereof with the mold resin 104 is heightened. Accordingly, the strength of the leads against pulling-out and the resistance of the device to moisture can be enhanced, and even the large-sized pellet can be packaged without the aforementioned problem.
Further, the present invention relates to a semiconductor device, and more particularly to techniques which are effective when applied to a semiconductor device in which a chip is supported by leads.
One semiconductor device wherein a chip is encapsulated with a resin package consists in supporting the chip in such a way that some of leads are extended under the chip so as to come in from a side surface and to go out to another side surface. The leads and the chip are insulated by a polyimide film, and the chip is bonded onto the polyimide film with a binder containing, for example, a thermoplastic resin. The bonding between the polyimide film and the leads is effected with a binder containing, for example, a thermoplastic resin.
Still further, the present invention relates to a lead frame for a semiconductor device wherein a semiconductor chip is mounted on the semiconductor chip placing parts of the inner leads of a tabless lead frame, the inner leads and the semiconductor chip are electrically connected by pieces of bonding wire, and the resultant structure is encapsulated with a resin mold member. More particularly, it relates to techniques which can prevent the leakage (short-circuiting) among the individual inner leads mentioned above.
In a semiconductor device conforming to a conventional resin mold package system, a semiconductor chip is mounted on a tab. With this system, it has been very difficult to encase a large chip, for example, the chip of a dynamic random access memory (DRAM) of 4 megabits in a package of 300 mils. It has therefore been proposed that an insulating film for mounting the semiconductor chip is bonded to the semiconductor chip placing parts of the inner leads of a tabless lead frame and has the semiconductor chip mounted thereon.